This invention relates generally to radiation imager arrays and to repair of shorts between the common electrode and other components in an imager, and in particular relates to determining the location of such shorts in an x-y addressed imager array.
Complex electronic devices are commonly formed on substrates in fabrication processes involving the deposition and patterning of multiple layers of conductive, semiconductive, and dielectric materials so as to form multiple individual electronic components. For example, large area imager arrays (e.g., having an area of about 25 cm.sup.2 or more) are commonly fabricated on a wafer and contain photodiodes and circuitry for reading the output of the photodiodes, such as address lines and switching components (e.g., thin film transistors (TFTs)). In such an array a common electrode layer extends over the top of almost the entire pixel array, with the off-the-wafer contacts for the common electrode being disposed at the four corners of the common electrode. Defects in such imager arrays can result from, among other causes, impurities in materials deposited to form the various components. One example of such an impurity-based defect is a short circuit between the common electrode and an underlying address line in the pixel array. Such short circuits disrupt the desired electrical connections between devices in the array and seriously degrade the performance of one or more of the individual electronic components on the wafer, often to the point of making an entire wafer unusable.
It is often difficult to locate a short circuit to the common electrode as the electrode extends over substantially the entire upper surface of the array, thus covering the entire length of each address line, including the address line to which it is shorted. Traditionally, a detailed visual inspection of the array has been required to attempt to locate the short circuit, a process that is time consuming and not always successful in locating the site of the short circuit. Procedures and imager structures that enable one to lessen the time to find the defect hasten the repair effort and thus reduce the overall cost of fabricating the array and improve the manufacturing yield of the array fabrication process.
The object of this invention is to provide a method to electrically localize the position of a short circuit in an electronic-array structure between the common electrode and other components in the array.
Another object of this invention is to provide a method for localizing the position of a short circuit in an array in which currents are measured from multiple contacts along opposite edges of the common electrode, and to provide a method for localizing the position of a short circuit in an array in which currents are measured from multiple contacts along adjoining sides of the common electrode.